Paste and sintered nickel hydroxide electrodes are known for use as positive electrodes for alkaline secondary batteries, such as a nickel-cadmium battery, a nickel-hydrogen battery and the like. In both paste and sintered electrodes, the positive active material utilized is nickel hydroxide, which serves as the main active component, and nickel or cobalt, which serve as an auxiliary electro-conductive component. The positive active material is contained on or in a substrate, for example, a foam nickel substrate for a paste electrode and a sintered nickel substrate for a sintered electrode.
Conventional alkaline secondary batteries as described above, however, have various defects. Conventional nickel hydroxide electrodes have a very slow absorption rate for hydrogen gas generated from the negative electrode at the time of charging due to the oxidation of the hydrogen gas to water. Therefore, in a sealed nickel-cadmium battery or a sealed nickel-hydrogen battery, the negative electrode is generally required to be provided with a larger capacity than the positive electrode in order to provide for the generation of oxygen gas prior to the generation of hydrogen gas and thereby the absorption of the hydrogen gas at the negative electrode by reduction. This results in an increase in the volume of the battery. However, there are limits to providing an excessive capacity to the negative electrode as compared to the capacity of the positive electrode since the volume of the battery to be produced is limited. Contrarily, if the capacity of the negative electrode is decreased, the volume or capacity of the battery is also decreased which is not desirable. Further, in a nickel-hydrogen battery, the hydrogen gas is emitted directly from the hydride of the negative electrode which increases the internal pressure in the battery. The released hydrogen gas is also flammable and susceptible to leaking.